The present invention relates to lenses, and, in particular, to lenses for use in sunglasses, which are externally treated in such a way to produce a new dual chromatic effect when viewed from the side opposed to the wearer. In particular, the present invention is directed at lenses that, when viewed from the side opposed to the wearer, reflect light in two different colors, one of which is reflected in a gradient manner.
In the prior art, chromatic effects have been generally achieved on lenses by depositing interference film on the outer surface of the lens. By choosing a film thickness properly, one can get a wide spectrum of reflected colors.
A common way to obtain a reflected color on the outer surface of a sunglass lens is to uniformly deposit a stack of dielectric films with alternative high and low refraction indexes. Such lenses are described in U.S. Pat. No. 3,679,291, which is hereby incorporated by reference.
Other chromatic lenses and methods for achieving the same are described in U.S. Pat. No. 4,160,584, which is hereby incorporated by reference. In one method, a uniform metallic layer is deposited over a substrate, and then a uniform dielectric material is deposited over the entire metallic layer. As described in U.S. Pat. No. 4,160,584, by depositing a thin transparent layer of a dielectric material on a thin transparent layer of metal, the light partially reflected changes its wavelength composition moving from the white light to a colored light of the spectrum depending on the thickness of the dielectric layer.
In a second method, also disclosed in U.S. Pat. No. 4,160,584, the metallic layer is gradiently deposited over the entire substrate and is then uniformly and entirely covered by a dielectric layer. In this case the outer surface will appear with a gradient colored reflection at the top becoming completely clear at the bottom.
In each of the two methods described above, the resultant lens produces a single, or single-gradient chromatic effect. That is, while colored, each of the lenses are of a single color. Various different materials for use in the metallic and dielectric layers, and the different colors that can be achieved, are described in U.S. Pat. No. 5,054,902, which is incorporated herein by reference.
The present invention is directed at providing a lens having a dual chromatic effect by utilizing at least one layer deposited in a gradient manner. The present invention is also directed at methods of manufacturing such lenses.